Articoli di riviste: "Nanoindentation"

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Jakes, Joseph E., e Donald S. Stone. "Best Practices for Quasistatic Berkovich Nanoindentation of Wood Cell Walls". Forests 12, n. 12 (3 dicembre 2021): 1696. http://dx.doi.org/10.3390/f12121696.

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For wood and forest products to reach their full potential as structural materials, experimental techniques are needed to measure mechanical properties across all length scales. Nanoindentation is uniquely suited to probe in situ mechanical properties of micrometer-scale features in forest products, such as individual wood cell wall layers and adhesive bondlines. However, wood science researchers most commonly employ traditional nanoindentation methods that were originally developed for testing hard, inorganic materials, such as metals and ceramics. These traditional methods assume that the tested specimen is rigidly supported, homogeneous, and semi-infinite. Large systematic errors may affect the results when these traditional methods are used to test complex polymeric materials, such as wood cell walls. Wood cell walls have a small, finite size, and nanoindentations can be affected by nearby edges. Wood cell walls are also not rigidly supported, and the cellular structure can flex under loading. Additionally, wood cell walls are softer and more prone to surface detection errors than harder inorganic materials. In this paper, nanoindentation methods for performing quasistatic Berkovich nanoindentations, the most commonly applied nanoindentation technique in forest products research, are presented specifically for making more accurate nanoindentation measurements in materials such as wood cell walls. The improved protocols employ multiload nanoindentations and an analysis algorithm to correct and detect errors associated with surface detection errors and structural compliances arising from edges and specimen-scale flexing. The algorithm also diagnoses other potential issues arising from dirty probes, nanoindenter performance or calibration issues, and displacement drift. The efficacy of the methods was demonstrated using nanoindentations in loblolly pine (Pinus taeda) S2 cell wall layers (S2) and compound corner middle lamellae (CCML). The nanoindentations spanned a large range of sizes. The results also provide new guidelines about the minimum size of nanoindentations needed to make reliable nanoindentation measurements in S2 and CCML.

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Mueller, Johannes, Karsten Durst, Dorothea Amberger e Matthias Göken. "Local Investigations of the Mechanical Properties of Ultrafine Grained Metals by Nanoindentations". Materials Science Forum 503-504 (gennaio 2006): 31–36. http://dx.doi.org/10.4028/www.scientific.net/msf.503-504.31.

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The mechanical properties of ultrafine-grained metals processed by equal channel angular pressing is investigated by nanoindentations in comparison with measurements on nanocrystalline nickel with a grain size between 20 and 400 nm produced by pulsed electrodeposition. Besides hardness and Young’s modulus measurements, the nanoindentation method allows also controlled experiments on the strain rate sensitivity, which are discussed in detail in this paper. Nanoindentation measurements can be performed at indentation strain rates between 10-3 s-1 and 0.1 s-1. Nanocrystalline and ultrafine-grained fcc metals as Al and Ni show a significant strain rate sensitivity at room temperature in comparison with conventional grain sized materials. In ultrafine-grained bcc Fe the strain rate sensitivity does not change significantly after severe plastic deformation. Inelastic effects are found during repeated unloading-loading experiments in nanoindentations.

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FANG, TE-HUA, WIN-JIN CHANG, CHAO-MING LIN e CHUN-CHIN CHANG. "CYCLIC NANOINDENTATION OF SEMICONDUCTOR AND METAL THIN FILMS". International Journal of Modern Physics B 23, n. 30 (10 dicembre 2009): 5639–47. http://dx.doi.org/10.1142/s0217979209053643.

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The nanoindentation technique was used to measure the hardness and Young's modulus of semiconductor and metal thin films on a Si(100) substrate under cyclic loading. The results showed that in all instances and at a constant cyclic load that the loading curves overlapped the previous unloading curve and had a small displacement after each cyclic nanoindentation. It was observed that the plastic energies of metal materials from the first loading–unloading cycle were much larger than that observed in semiconductor materials. Furthermore, the hardness and Young's modulus of the thin films decreased when the number of cyclic nanoindentations was increased. The effect of the cyclic loading on the hardness and Young's modulus of semiconductor material was much larger than that of the metal material. Young's modulus, the hardness and the contact stiffness of thin films conform to the relationship that Young's modulus was proportional to the contact stiffness and the square root of the thin film's hardness.

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Pero, Renato, Giovanni Maizza, Roberto Montanari e Takahito Ohmura. "Nano-Indentation Properties of Tungsten Carbide-Cobalt Composites as a Function of Tungsten Carbide Crystal Orientation". Materials 13, n. 9 (5 maggio 2020): 2137. http://dx.doi.org/10.3390/ma13092137.

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Tungsten carbide-cobalt (WC-Co) composites are a class of advanced materials that have unique properties, such as wear resistance, hardness, strength, fracture-toughness and both high temperature and chemical stability. It is well known that the local indentation properties (i.e., nano- and micro-hardness) of the single crystal WC particles dispersed in such composite materials are highly anisotropic. In this paper, the nanoindentation response of the WC grains of a compact, full-density, sintered WC-10Co composite material has been investigated as a function of the crystal orientation. Our nanoindentation survey has shown that the nanohardness was distributed according to a bimodal function. This function was post-processed using the unique features of the finite mixture modelling theory. The combination of electron backscattered diffraction (EBSD) and statistical analysis has made it possible to identify the orientation of the WC crystal and the distinct association of the inherent nanoindentation properties, even for a small set (67) of nanoindentations. The proposed approach has proved to be faster than the already existing ones and just as reliable, and it has confirmed the previous findings concerning the relationship between crystal orientation and indentation properties, but with a significant reduction of the experimental data.

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Randall, Nicholas X., Matthieu Vandamme e Franz-Josef Ulm. "Nanoindentation analysis as a two-dimensional tool for mapping the mechanical properties of complex surfaces". Journal of Materials Research 24, n. 3 (marzo 2009): 679–90. http://dx.doi.org/10.1557/jmr.2009.0149.

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Instrumented indentation (referred to as nanoindentation at low loads and low depths) has now become established for the single point characterization of hardness and elastic modulus of both bulk and coated materials. This makes it a good technique for measuring mechanical properties of homogeneous materials. However, many composite materials are composed of material phases that cannot be examined in bulk form ex situ (e.g., carbides in a ferrous matrix, calcium silicate hydrates in cements, etc.). The requirement for in situ analysis and characterization of chemically complex phases obviates conventional mechanical testing of large specimens representative of these material components. This paper will focus on new developments in the way that nanoindentation can be used as a two-dimensional mapping tool for examining the properties of constituent phases independently of each other. This approach relies on large arrays of nanoindentations (known as grid indentation) and statistical analysis of the resulting data.

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Donaldson, Laurie. "Novel nanoindentation". Materials Today 16, n. 9 (settembre 2013): 310. http://dx.doi.org/10.1016/j.mattod.2013.08.007.

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Rar, Andrei, G. M. Pharr, W. C. Oliver, E. Karapetian e Sergei V. Kalinin. "Piezoelectric nanoindentation". Journal of Materials Research 21, n. 3 (1 marzo 2006): 552–56. http://dx.doi.org/10.1557/jmr.2006.0081.

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Piezoelectric nanoindentation (PNI) has been developed to quantitatively address electromechanical coupling and pressure-induced dynamic phenomena in ferroelectric materials on the nanoscale. In PNI, an oscillating voltage is applied between the back side of the sample and the indenter tip, and the first harmonic of bias-induced surface displacement at the area of indenter contact is detected. PNI is implemented using a standard nanoindentation system equipped with a continuous stiffness measurement system. The piezoresponse of polycrystalline lead zirconate titanate (PZT) and BaTiO3 piezoceramics was studied during a standard nanoindentation experiment. For PZT, the response was found to be load independent, in agreement with theoretical predictions. In polycrystalline barium titanate, a load dependence of the piezoresponse was observed. The potential of piezoelectric nanoindentation for studies of phase transitions and local structure-property relations in piezoelectric materials is discussed.

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Minorl, A. M., E. A. Stach e J. W. Morris. "Quantitative In-Situ Nanoindentation of Thin Films in a Transmission Electron Microscope". Microscopy and Microanalysis 7, S2 (agosto 2001): 912–13. http://dx.doi.org/10.1017/s1431927600030634.

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A unique in situ nanoindentation stage has been built and developed at the National Center for Electron Microscopy in Berkeley, CA. By using piezoceramic actuators to finely position a 3-sided, boron-doped diamond indenter, we are able to image in real time the nanoindentation induced deformation of thin films. Recent work has included the force-calibration of the indenter, using silicon cantilevers to establish a relationship between the voltage applied to the piezoactuators, the displacement of the diamond tip, and the force generated.In this work, we present real time, in situ TEM observations of the plastic deformation of Al thin films grown on top of lithographically-prepared silicon substrates. The in situ nanoindentations require a unique sample geometry (see Figure 1) in which the indenter approaches the specimen normal to the electron beam. in order to meet this requirement, special wedge-shaped silicon samples were designed and microfabricated so that the tip of the wedge is sharp enough to be electron transparent.

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Zhou, Hong Xiu, Ming Lei Li, Neng Dong Duan, Bo Wang, Zhi Feng Shi, Ji Lei Lyu e Guo Xin Chen. "Nanotwinned Surface on a Ternary Titanium Alloy with Increased Hardness Induced under Nanoindentations". Materials Science Forum 874 (ottobre 2016): 323–27. http://dx.doi.org/10.4028/www.scientific.net/msf.874.323.

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A nanotwinned surface is formed on a titanium alloy under nanoindentations. Prior to nanoindentation, blocks of a ternary titanium alloy are machined by chemical mechanical polishing. The surface roughness Ra and peak-to-valley values are 1.135 nm and 8.82 nm, respectively. The hardness in the indented surface is greatly increased, indicated from the load-displacement curves compared to the polished surfaces. Nanotwins are confirmed using transmission electron microscopy. The nanotwinned surface is uniformly generated by nanoindentations at room temperature, which is different from previous findings, in which high temperature, high pressure, or chemical reagents are usually used. The nanotwinned surface is produced by pure mechanical stress, neither material removal nor addition.

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Le Bourhis, E., G. Patriarche, L. Largeau e J. P. Rivière. "Polarity-induced changes in the nanoindentation response of GaAs". Journal of Materials Research 19, n. 1 (gennaio 2004): 131–36. http://dx.doi.org/10.1557/jmr.2004.19.1.131.

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We studied the polarity-induced changes in the nanoindentation response of GaAs{111}. The nanoindentations were made under a large range of loads (Fmax between 0.2 mN and 50 mN) at room temperature on {111} faces of A (Ga) or B (As) character. The loading–unloading curves were compared first, with special attention addressed to pop-in events and hardness values (reported previously for microindentation). Transmission electron microscopy was used to observe the nanoindentation structures generated at the two polar surfaces. The size of the dense plastic zone generated around the indent site was found to increase linearly with √Fmax and similarly for both polar surfaces. The indentation rosettes possess a threefold symmetry with arms developed along the <110> directions parallel to the surface. Sizes were found to be very close for both polar surfaces and the entire load range. For an A-polar face, the rosette arms are constituted by two arms: a long arm (LA, α dislocations) and a short arm (β dislocations). At the B surface, only the LA (β dislocations) are formed. Furthermore, microtwinning was observed only for an A-polar face, similar to previous observations of anisotropic microtwinning at GaAs(001) surfaces.

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Kaufman, Jessica D., Gregory J. Miller, Elise F. Morgan e Catherine M. Klapperich. "Time-dependent mechanical characterization of poly(2-hydroxyethyl methacrylate) hydrogels using nanoindentation and unconfined compression". Journal of Materials Research 23, n. 5 (maggio 2008): 1472–81. http://dx.doi.org/10.1557/jmr.2008.0185.

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Hydrogels pose unique challenges to nanoindentation including sample preparation, control of experimental parameters, and limitations imposed by mechanical testing instruments and data analysis originally intended for harder materials. The artifacts that occur during nanoindentation of hydrated samples have been described, but the material properties obtained from hydrated nanoindentation have not yet been related to the material properties obtained from macroscale testing. To evaluate the best method for correlating results from microscale and macroscale tests of soft materials, nanoindentation and unconfined compression stress-relaxation tests were performed on poly-2-hydroxyethyl methacrylate (pHEMA) hydrogels with a range of cross-linker concentrations. The nanoindentation data were analyzed with the Oliver–Pharr elastic model and the Maxwell–Wiechert (j = 2) viscoelastic model. The unconfined compression data were analyzed with the Maxwell–Wiechert model. This viscoelastic model provided an excellent fit for the stress-relaxation curves from both tests. The time constants from nanoindentation and unconfined compression were significantly different, and we propose that these differences are due to differences in equilibration time between the microscale and macroscale experiments and in sample geometry. The Maxwell–Wiechert equilibrium modulus provided the best agreement between nanoindentation and unconfined compression. Also, both nanoindentation analyses showed an increase in modulus with each increasing cross-linker concentration, validating that nanoindentation can discriminate between similar, low-modulus, hydrated samples.

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Dragatogiannis, Dimitrios A., Elias P. Koumoulos, Ioannis A. Kartsonakis e Costas A. Charitidis. "Deformation mechanism during nanoindentation creep and corrosion resistance of Zn". International Journal of Structural Integrity 7, n. 1 (1 febbraio 2016): 47–69. http://dx.doi.org/10.1108/ijsi-07-2014-0034.

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Purpose – The study of nanoindentation as a reliable method to extract creep properties as well as for fundamental understanding of deformation mechanisms at small length scales is an open interesting field. The observed creep behavior is attributed to time-dependent plastic deformation based on loading rates. There is a lot of work in the field of nanoindentation in order to understand the dynamic effects on nanomechanical properties. The paper aims to discuss these issues. Design/methodology/approach – The deformation mechanism is investigated under two experimental approaches (high and low loading rates, respectively) during nanoindentation. The effect of loading rate in the nanomechanical properties, during nanoindentation creep of zinc layer on hot dip galvanized (HDG) steel, is discussed through nanoindentation. Findings – Analysis of this research effort is emphasized on nanoindentation stress exponent, a critical parameter for the life time and reliability of nano/micro-materials and systems. The corrosion resistance was studied by electrochemical impedance spectroscopy (EIS) and localized EIS. Originality/value – The study of nanoindentation as a reliable method to extract creep properties as well as for fundamental understanding of deformation mechanisms at small length scales is an open interesting field. The observed creep behavior is attributed to time-dependent plastic deformation based on loading rates. The deformation mechanism is investigated under two experimental approaches (high and low loading rates, respectively) during nanoindentation. The effect of loading rate in the nanomechanical properties, during nanoindentation creep of zinc layer on HDGsteel, is discussed through nanoindentation. Analysis of this research effort is emphasized on nanoindentation stress exponent, a critical parameter for the life time and reliability of nano/micro- materials and systems. The corrosion resistance was studied by EIS and localized EIS.

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KUMAR, AMIT, e KAIYANG ZENG. "ALTERNATIVE METHODS TO EXTRACT THE HARDNESS AND ELASTIC MODULUS OF THIN FILMS FROM NANOINDENTATION LOAD-DISPLACEMENT DATA". International Journal of Applied Mechanics 02, n. 01 (marzo 2010): 41–68. http://dx.doi.org/10.1142/s1758825110000445.

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This paper presents alternative analysis methodologies to extract the elastic modulus and hardness of the ultra-thin films from nanoindentation load-displacement data, especially when the film thickness is only few hundred nanometers or less. At such film thickness, the conventional analysis methods for nanoindentation usually do not give accurate film properties due to the substrate effect. The new methods are capable to show how to determine the film-only properties and how the substrates affect the nanoindentation measurement, especially for ultra thin films. These methods give accurate results for nanoindentation of various metallic, ceramic and polymeric films. It also reveals the differences between the use of high-resolution nanoindentation set-up and normal nanoindentation set-up on the same films. The relationships between the mechanical properties and film thickness are also discussed.

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Yu, Yunhong, Gang Xu, Tianling Wang, Huimin Chen, Houzhi Wang e Jun Yang. "Analysis of Nanoindentation Test Results of Asphalt Mixture with Different Gradations". Applied Sciences 11, n. 17 (29 agosto 2021): 7992. http://dx.doi.org/10.3390/app11177992.

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Nanoindentation has been applied in the field of asphalt mixtures, but, at the nano-scale, changes in the composition of the mixture and material properties can have a significant impact on the results. Therefore, it is necessary to investigate the feasibility of nanoindentation tests on different types of asphalt mixtures with different gradations and the influence of material properties and test methods on nanoindentation results. In this paper, the nanoindentation test results on three kinds of asphalt mixture (AC-13, SMA-13, and OGFC-13) with different aggregate gradations were investigated. The load-displacement curves and moduli obtained from the nanoindentation tests were analyzed. In addition, nanoindentation tests were carried out before and after polishing with different ratios of filler and asphalt (RFA) (0.8–1.6). On this basis, the morphology of asphalt specimens with different RFAs is observed by scanning electron microscopy (SEM) imaging. The results indicate that using the nanoindentation test to characterize the mechanical behavior of asphalt mixture, the confidence level of the dense-graded mixture is low, and non-dense-graded mixtures are used as much as possible. Moreover, results illustrate that the nanoindentation modulus tends to increase as the RFA increases. and the SEM chart shows that the higher the mineral powder content in the mastic, the more complex the bitumen and mineral powder interaction surface, confirming the influence of mineral powder content on the nanoindentation test results. Furthermore, the effect of polishing is almost insignificant.

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Basu, Sandip, Alexander Moseson e Michel W. Barsoum. "On the determination of spherical nanoindentation stress–strain curves". Journal of Materials Research 21, n. 10 (ottobre 2006): 2628–37. http://dx.doi.org/10.1557/jmr.2006.0324.

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Instrumented nanoindentation experiments, especially with sharp tips, are a well-established technique to measure the hardness and moduli values of a wide range of materials. However, and despite the fact that they can accurately delineate the onset of the elasto-plastic transition of solids, spherical nanoindentation experiments are less common. In this article we propose a technique in which we combine (i) the results of continuous stiffness measurements with spherical indenters – with radii of 1 μm and/or 13.5 μm, (ii) Hertzian theory, and (iii) Berkovich nanoindentations, to convert load/depth of indentation curves to their corresponding indentation stress–strain curves. We applied the technique to fused silica, aluminum, iron and single crystals of sapphire and ZnO. In all cases, the resulting indentation stress–strain curves obtained clearly showed the details of the elastic-to-plastic transition (i.e., the onset of yield, and, as important, the steady state hardness values that were comparable with the Vickers microhardness values obtained on the same surfaces). Furthermore, when both the 1 μm and 13.5 μm indenters were used on the same material, for the most part, the indentation stress–strain curves traced one trajectory. The method is versatile and can be used over a large range of moduli and hardness values.

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Nagy, Péter M., P. Horváth, Gábor Pető e Erika Kálmán. "Nanoindentation of Silicon". Materials Science Forum 604-605 (ottobre 2008): 29–36. http://dx.doi.org/10.4028/www.scientific.net/msf.604-605.29.

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The nanoindentation behaviours of single crystalline silicon samples has gained wide attention in recent years, because of the anomaly effects in the loading curve, caused by the pressure induced phase transformation of silicon. To further enlighten the phenomenon bulk, ion-implanted, single crystalline Si samples have been studied by nanoindentation and by atomic force microscopy. The implantation of Si wafers was carried out by P+ ions at 40 KeV accelerating voltage and 80 ions/cm2 dose, influencing the defect density and structure of the Si material in shallow depth at the surface. Our experiments provide Young’s modulus and hardness data measured with Berkovich-, spherical- and cube corner indenters, statistics of the pop-in and pop-out effects in the loading- and unloading process, and interesting results about the piling-up behaviour of the Si material.

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Cakmak, Umut D., Thomas Schöberl e Zoltan Major. "Nanoindentation of polymers". Meccanica 47, n. 3 (4 novembre 2011): 707–18. http://dx.doi.org/10.1007/s11012-011-9481-6.

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Bull, S. J. "Nanoindentation of coatings". Journal of Physics D: Applied Physics 38, n. 24 (2 dicembre 2005): R393—R413. http://dx.doi.org/10.1088/0022-3727/38/24/r01.

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Csach, Kornel, Jozef Miškuf, Alena Juríková, Maria Hurakova, Václav Ocelík e Jeff T. M. de Hosson. "Nanoindentation in Metallic Glasses with Different Plasticity". Key Engineering Materials 662 (settembre 2015): 19–22. http://dx.doi.org/10.4028/www.scientific.net/kem.662.19.

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Nanoindentation and thermomechanical experiments on three types of metallic glasses with different glass forming ability were carried out. The nanoindentation behaviour at room temperature was associated with the creep at elevated temperatures. Different discontinuity populations and their shape observed on the nanoindentation loading curves were compared with morphology of plastic deformed indent regions. The influence of the differences in thermal stability of studied alloys on the nanoindentation in these alloys were studied as well.

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Chang, Li, e Liang Chi Zhang. "A Note on the Unloading Behavior of Silicon Subjected to Nanoindentation". Advanced Materials Research 76-78 (giugno 2009): 398–403. http://dx.doi.org/10.4028/www.scientific.net/amr.76-78.398.

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It is known that silicon, during nanoindentation unloading, undergoes various phase transformations beneath the indenter. Investigations into the details are however not available. This paper studies the unloading behavior of silicon subjected to cyclic nanoindentations. The results show that the elastic unloading behavior of the material can be described by a power relationship, P = α∙hm, where P is the load, h is the elastic displacement, and α and m are material constants. It was found that the values of α and m were almost independent of the phase transition events, indicating that the elastic response of the material is mostly governed by the mechanical properties of Si-I phase while the influence of the phase transformations is negligible.

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Kanders, U., e K. Kanders. "Nanoindentation Response analysis of Thin Film Substrates-I: Strain Gradient-Divergence Approach". Latvian Journal of Physics and Technical Sciences 54, n. 1 (1 febbraio 2017): 66–76. http://dx.doi.org/10.1515/lpts-2017-0007.

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Abstract Nanoindentation is a widely-used method for sensitive exploration of the mechanical properties of micromechanical systems. We derive a simple empirical analysis technique to extract stress-strain field (SSF) gradient and divergence representations from nanoindentation data sets. Using this approach, local SSF gradients and structural heterogeneities can be discovered to obtain more detail about the sample’s microstructure, thus enhancing the analytic capacity of the nanoindentation technique. We demonstrate the application of the SSF gradient-divergence analysis approach to nanoindentation measurements of bulk silicon.

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Herbert, E. G., W. C. Oliver, A. Lumsdaine e G. M. Pharr. "Measuring the constitutive behavior of viscoelastic solids in the time and frequency domain using flat punch nanoindentation". Journal of Materials Research 24, n. 3 (marzo 2009): 626–37. http://dx.doi.org/10.1557/jmr.2009.0089.

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The purpose of this work is to further develop experimental methodologies using flat punch nanoindentation to measure the constitutive behavior of viscoelastic solids in the frequency and time domain. The reference material used in this investigation is highly plasticized polyvinylchloride (PVC) with a glass transition temperature of −17 °C. The nanoindentation experiments were conducted using a 983-μm-diameter flat punch. For comparative purposes, the storage and loss modulus obtained by nanoindentation with a 103-μm-diameter flat punch and dynamic mechanical analysis are also presented. Over the frequency range of 0.01–50 Hz, the storage and loss modulus measured using nanoindentation and uniaxial compression is shown to be in excellent agreement. The creep compliance function measured using a constant stress test performed in uniaxial compression and flat punch nanoindentation is also shown to correlate well over nearly 4 decades in time. In addition, the creep compliance function predicted from nanoindentation data acquired in the frequency domain is shown to correlate strongly with the creep compliance function measured in the time domain. Time–temperature superposition of nanoindentation data taken at 5, 10, 15, and 22 °C shows the sample is not thermorheologically simple, and thus the technique cannot be used to expand the mechanical characterization of this material. Collectively, these results clearly demonstrate the ability of flat punch nanoindentation to accurately and precisely determine the constitutive behavior of viscoelastic solids in the time and frequency domain.

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Naimi-Jamal, M. R., e G. Kaupp. "Quantitative evaluation of nanoindents: Do we need more reliable mechanical parameters for the characterization of materials?" International Journal of Materials Research 96, n. 11 (1 novembre 2005): 1226–36. http://dx.doi.org/10.1515/ijmr-2005-0214.

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Abstract Various sources of errors in the standard procedure according to the ISO 14577 draft for the iteration of elastic modulus and hardness of solid materials, with reference to fused quartz with its particular and unique indentation response, are pointed out on the basis of practical examples. Similar objections exist towards the use of the S 2 F N – 1 parameter, where S is the stiffness and F N is the normal force. It is suggested to use unambiguous mechanic characterization (at least additionally) by quantitative analysis of the loading curves in nanoindentations. These exhibit a general dependence between normal force and (displacement)3/2, the proportionality constant k being a non-iterated nanoindentation coefficient with dimension [force/length3/2] and unit [μN/nm3/2] that depends on the indenter tip geometry (pyramidal or conospherical) and is a characteristic material’s property. The validity has been demonstrated for virtually all types of materials (metals, semimetals, oxides, salts, organic molecular crystals, polymers) independent of their different bonding states. Pressure-induced phase transitions are detected by kinks in the linear plots for the loading curves well in the nanoindentation region. Crystalline materials, such as strontium titanate, exhibit far-reaching anisotropic effects along lattice axes that would strongly forbid the reference to an amorphous standard. The nanoindentation coefficient characterizes the different polymorphs and the face anisotropies. Another unambiguous mechanical characterization is given by the full work of indentation (as differentiated from the less secure plastic work of indentation). It also characterizes the face anisotropies with high precision for a given indenter as it is found proportional to (normal force)3/2, which allows for useful extrapolations.

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Shu, S. Q., Y. Yang, T. Fu, C. S. Wen e J. Lu. "Can Young’s modulus and hardness of wire structural materials be directly measured using nanoindentation?" Journal of Materials Research 24, n. 3 (marzo 2009): 1054–58. http://dx.doi.org/10.1557/jmr.2009.0079.

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In recent studies, nanoindentation experiments combined with the Oliver and Pharr method (OP method) are frequently used to measure the mechanical properties of “one-dimensional” structural materials (micro/nanowires and nanobelts) regardless of the corresponding assumptions of the OP method. This article reports the numerical simulation studies of the nanoindentations of wire structural materials on elastic-plastic substrates using dimensional analysis and the finite element method. We find that the measured hardness and Young’s modulus of wire structural materials are significantly influenced by their geometries and indenters as well as the mechanical properties of substrates and wires.

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Yeo, Chang-Dong, e Andreas A. Polycarpou. "A correction to the nanoindentation technique for ultrashallow indenting depths". Journal of Materials Research 22, n. 9 (settembre 2007): 2359–62. http://dx.doi.org/10.1557/jmr.2007.0300.

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A correction to the nanoindentation technique taking into account the elastic recovery at extremely shallow contact depths was proposed. Using a high-sensitivity nanoindentation system with a sharp indenting tip, the magnitude of the elastic recovery could be obtained directly from very low-force load–unload curves, which was then used to correct the contact area used for hardness measurements. Nanoindentation experiments were performed on a standard fused quartz sample and, compared to standard nanoindentation techniques, the proposed method was found to be more accurate at ultrashallow indenting depths of <3 nm.

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Nazemian, M., M. Chamani e M. Baghani. "A Combined Experimental and Numerical Study of the Effect of Surface Roughness on Nanoindentation". International Journal of Applied Mechanics 11, n. 07 (agosto 2019): 1950070. http://dx.doi.org/10.1142/s1758825119500704.

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Gold and copper thin films are widely used in microelectromechanical system (MEMS) and nanoelectromechanical system (NEMS) devices. Nanoindentation has been developed in mechanical characterization of thin films in recent years. Several researchers have examined the effect of surface roughness on nanoindentation results. It is proved that the surface roughness has great importance in nanoindentation of thin films. In this paper, the surface topography of thin films is simulated using the extracted data from the atomic force microscopy (AFM) images. Nanoindentation on a rough surface is simulated using a three-dimensional finite-element model. The results are compared with the results of finite-element analysis on a smooth surface and the experimental results. The results revealed that the surface roughness plays a key role in nanoindentation of thin films, especially at low indentation depths. There was good compatibility between the results of finite-element simulation on the rough surface and those of experiments. It is observed that on rough films, at low indentation depths, the geometry of the location where the nanoindentation is performed is of major importance.

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27

Raupach, Kristina, Andreas Bogner, Michael Vogel, Engin Kotan e Frank Dehn. "Systematic Experimental Investigation into the Determination of Micromechanical Properties of Hardened Cement Paste Using Nanoindentation—Opportunities and Limitations". Materials 16, n. 4 (8 febbraio 2023): 1420. http://dx.doi.org/10.3390/ma16041420.

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The nanoindentation technique is already widely applied in the mechanical characterization of the microstructure of thin films with respect to different materials. Generally, by means of nanoindentation, the hardness and the elastic modulus of materials can be determined with high precision. The focus of these analyses is usually on the materials from the metal, ceramic, and plastics processing industry. The application of nanoindentation in construction science, especially in concrete technology, is a relatively new field of investigation. This study deals with the basic application of nanoindentation for the mechanical characterization of hardened cement paste. In particular, the effects of sample preparation and the selection of the nanoindentation measurement parameters on the obtained results are the main subjects of this investigation. The results re intended to show the opportunities and limitations of analyzing a heterogeneous material such as hardened cement paste. The findings are used to assess the suitability of the nanoindentation method for investigating durability-related damage (e.g., due to freeze–thaw or alkali–silica reaction) in concrete.

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28

Long, Xu, Xiaodi Zhang, Wenbin Tang, Shaobin Wang, Yihui Feng e Chao Chang. "Calibration of a Constitutive Model from Tension and Nanoindentation for Lead-Free Solder". Micromachines 9, n. 11 (20 novembre 2018): 608. http://dx.doi.org/10.3390/mi9110608.

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It is challenging to evaluate constitutive behaviour by using conventional uniaxial tests for materials with limited sizes, considering the miniaturization trend of integrated circuits in electronic devices. An instrumented nanoindentation approach is appealing to obtain local properties as the function of penetration depth. In this paper, both conventional tensile and nanoindentation experiments are performed on samples of a lead-free Sn–3.0Ag–0.5Cu (SAC305) solder alloy. In order to align the material behaviour, thermal treatments were performed at different temperatures and durations for all specimens, for both tensile experiments and nanoindentation experiments. Based on the self-similarity of the used Berkovich indenter, a power-law model is adopted to describe the stress–strain relationship by means of analytical dimensionless analysis on the applied load-penetration depth responses from nanoindentation experiments. In light of the significant difference of applied strain rates in the tensile and nanoindentation experiments, two “rate factors” are proposed by multiplying the representative stress and stress exponent in the adopted analytical model, and the corresponding values are determined for the best predictions of nanoindentation responses in the form of an applied load–indentation depth relationship. Eventually, good agreement is achieved when comparing the stress–strain responses measured from tensile experiments and estimated from the applied load–indentation depth responses of nanoindentation experiments. The rate factors ψ σ and ψ n are calibrated to be about 0.52 and 0.10, respectively, which facilitate the conversion of constitutive behaviour from nanoindentation experiments for material sample with a limited size.

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29

Cohen, Sidney R., e Estelle Kalfon-Cohen. "Dynamic nanoindentation by instrumented nanoindentation and force microscopy: a comparative review". Beilstein Journal of Nanotechnology 4 (29 novembre 2013): 815–33. http://dx.doi.org/10.3762/bjnano.4.93.

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Viscoelasticity is a complex yet important phenomenon that drives material response at different scales of time and space. Burgeoning interest in nanoscale dynamic material mechanics has driven, and been driven by two key techniques: instrumented nanoindentation and atomic force microscopy. This review provides an overview of fundamental principles in nanoindentation, and compares and contrasts these two techniques as they are used for characterization of viscoelastic processes at the nanoscale.

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30

Wasmer, Kilian, Cédric Pouvreau, Jean-Marc Breguet, Johann Michler, Daniel Schulz e Jacques Henri Giovanola. "Nanoindentation cracking in gallium arsenide: Part I. In situ SEM nanoindentation". Journal of Materials Research 28, n. 20 (22 ottobre 2013): 2785–98. http://dx.doi.org/10.1557/jmr.2013.252.

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31

Nguyen, Pham T. N., Fazilay Abbès, Jean-Sébastien Lecomte, Christophe Schuman e Boussad Abbès. "Inverse Identification of Single-Crystal Plasticity Parameters of HCP Zinc from Nanoindentation Curves and Residual Topographies". Nanomaterials 12, n. 3 (18 gennaio 2022): 300. http://dx.doi.org/10.3390/nano12030300.

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This paper investigates the orientation-dependent characteristics of pure zinc under localized loading using nanoindentation experiments and crystal plasticity finite element (CPFEM) simulations. Nanoindentation experiments on different grain orientations exhibited distinct load–depth responses. Atomic force microscopy revealed two-fold unsymmetrical material pile-up patterns. Obtaining crystal plasticity model parameters usually requires time-consuming micromechanical tests. Inverse analysis using experimental and simulated loading–unloading nanoindentation curves of individual grains is commonly used, however the solution to the inverse identification problem is not necessarily unique. In this study, an approach is presented allowing the identification of CPFEM constitutive parameters from nanoindentation curves and residual topographies. The proposed approach combines the response surface methodology together with a genetic algorithm to determine an optimal set of parameters. The CPFEM simulations corroborate with measured nanoindentation curves and residual profiles and reveal the evolution of deformation activity underneath the indenter.

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32

Bontempi, Marco, Gregorio Marchiori, Mauro Petretta, Rosario Capozza, Brunella Grigolo, Gianluca Giavaresi e Alessandro Gambardella. "Nanomechanical Mapping of Three Dimensionally Printed Poly-ε-Caprolactone Single Microfibers at the Cell Scale for Bone Tissue Engineering Applications". Biomimetics 8, n. 8 (16 dicembre 2023): 617. http://dx.doi.org/10.3390/biomimetics8080617.

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Poly-ε-caprolactone (PCL) has been widely used in additive manufacturing for the construction of scaffolds for bone tissue engineering. However, its use is limited by its lack of bioactivity and inability to induce cell adhesion, hence limiting bone tissue regeneration. Biomimicry is strongly influenced by the dynamics of cell–substrate interaction. Thus, characterizing scaffolds at the cell scale could help to better understand the relationship between surface mechanics and biological response. We conducted atomic force microscopy-based nanoindentation on 3D-printed PCL fibers of ~300 µm thickness and mapped the near-surface Young’s modulus at loading forces below 50 nN. In this non-disruptive regime, force mapping did not show clear patterns in the spatial distribution of moduli or a relationship with the topographic asperities within a given region. Remarkably, we found that the average modulus increased linearly with the logarithm of the strain rate. Finally, a dependence of the moduli on the history of nanoindentation was demonstrated on locations of repeated nanoindentations, likely due to creep phenomena capable of hindering viscoelasticity. Our findings can contribute to the rational design of scaffolds for bone regeneration that are capable of inducing cell adhesion and proliferation. The methodologies described are potentially applicable to various tissue-engineered biopolymers.

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33

Kovář, Jaroslav, Vladimír Fuis e Jan Tomáštík. "INFLUENCING THE INDENTATION CURVES BY THE BLUNTNESS OF THE BERKOVICH INDENTER AT THE FEM MODELLING". Acta Polytechnica CTU Proceedings 27 (11 giugno 2020): 131–35. http://dx.doi.org/10.14311/app.2020.27.0131.

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The influence of the Berkovich indenter bluntness on the indentation curves at nanoindentation test of fused silica is determined by the FEM (finite element method) in this paper. The Berkovich indenter, which is mostly used for the nanoindentation test, was assumed for calculations. The indenter is always blunted in real tests. The bluntness of the indenter has an influence on the results of the nanoindentation test. The combination of the nanoindentation test and the FE modelling can be used for the calculation of the parameters of fused silica plasticity and estimation of the bluntness of the indenter. In this paper, the FEM was used for calculating of the indentation curves. Two cases of bluntness were assumed. The curves for ideally sharp or blunted indenter were determined. The results of these calculations showed that the indentation curves are dependent on the bluntness of the Berkovich indenter. The greatest relative influence of the nanoindentation curves by the bluntness is in the area of small values of the indenter displacement. The impact of assuming blunted indenter to calculated parameters of plasticity was assessed. It is often difficult to measure the bluntness of the indenter but it has an influence on the results of the nanoindentation test and should be included into calculations to make it more precise.

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34

Tsui, T. Y., W. C. Oliver e G. M. Pharr. "Influences of stress on the measurement of mechanical properties using nanoindentation: Part I. Experimental studies in an aluminum alloy". Journal of Materials Research 11, n. 3 (marzo 1996): 752–59. http://dx.doi.org/10.1557/jmr.1996.0091.

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The influence of applied stress on the measurement of hardness and elastic modulus using nanoindentation methods has been experimentally investigated using special specimens of aluminum alloy 8009 to which controlled stresses could be applied by bending. When analyzed according to standard methods, the nanoindentation data reveal changes in hardness with stress similar to those observed in conventional hardness tests. However, the same analysis shows that the elastic modulus changes with stress by as much as 10%, thus suggesting that the analysis procedure is somehow deficient. Comparison of the real indentation contact areas measured optically to those determined from the nanoindentation data shows that the apparent stress dependence of the modulus results from an underestimation of the contact area by the nanoindentation analysis procedures.

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35

Colak, Ozgen U., e Ardavan Zandiatashbar. "Fabrication of Graphene Platelet (GPL)-Epoxy Nanocomposites and Characterization by Nanoindentation". Advanced Materials Research 445 (gennaio 2012): 809–14. http://dx.doi.org/10.4028/www.scientific.net/amr.445.809.

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Main objective of this work is to manufacture the graphene platelet (GPL)-epoxy nanocomposite and to characterize the nanocomposite using nanoindentation technique. Thermal reduction of graphite oxide is the method used to obtain bulk quantities of graphene platelets (GPL) which comprise multiple graphene sheets. Dispersion of GPL in epoxy matrix is done with sonication and high speed shear mixing is used for mixing curing agent and resin. Following the manufacturing of graphene platelet-epoxy nanocomposites, characterization of the material was performed by nanoindentation. Nanoindentation experiments are performed under load or displacement control at different load/displacement rates to investigate rate dependent behavior of the nanocomposite. The primary mechanical properties obtained from the nanoindentation tests which are the hardness and the elasticity modulus are determined.

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36

Chang, Hyung Jun, Heung Nam Han e Marc Fivel. "Multiscale Modelling of Nanoindentation". Key Engineering Materials 345-346 (agosto 2007): 925–30. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.925.

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Nanoindentation is an interesting technique used to probe the local mechanical properties of a material. Although this test has been widely used and developed over the world during the past few years, it remains a lot of uncertainties regarding the interpretation of nanoindentation data. In this study, we propose to simulate the nanoindentation test of FCC single crystals like Cu or Ni using three numerical models. At the lowest scale, molecular dynamics simulations give details of the nucleation of the first dislocations induced by the indentation. At an intermediate scale, discrete dislocation dynamics simulations are performed to study the evolution of the dislocation microstructure during the loading. Finally, at the upper scale, 3D finite element modelling using crystal plasticity constitutive equations give a continuum description of the indentation induced plasticity. It is shown how the different models are interconnected together.

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37

Sondergeld, Carl H., e Chandra S. Rai. "A Guide to Nanoindentation". Petrophysics – The SPWLA Journal of Formation Evaluation and Reservoir Description 63, n. 5 (1 ottobre 2022): 576–90. http://dx.doi.org/10.30632/pjv63n5-2022a1.

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Nanoindentation is a new technology slowly gaining acceptance in the oil and gas community. In an effort to accelerate its adoption, we review its capabilities and applications. The technology was developed to study thin film and semiconductor properties. It became attractive to the oil and gas industry when focus switched to unconventional shales. Because of the friability and instability of shales, retrieving core plugs for standard measurements became impossible in many cases. Nanoindentation is perfectly adapted to measuring the properties of fine-grained materials and material fragments. We document how nanoindentation can be used to measure Young’s modulus, hardness, shear modulus, anisotropy, creep, and fracture toughness and to examine the fluid sensitivity of these properties in shale.

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38

Adeoye, M. O., e O. O. Adewoye. "Nanoindentation Study on Tourmaline". Journal of Minerals and Materials Characterization and Engineering 05, n. 01 (2006): 63–72. http://dx.doi.org/10.4236/jmmce.2006.51004.

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39

Mayo, M. J., R. W. Siegel, Y. X. Liao e W. D. Nix. "Nanoindentation of nanocrystalline ZnO". Journal of Materials Research 7, n. 4 (aprile 1992): 973–79. http://dx.doi.org/10.1557/jmr.1992.0973.

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A number of nanocrystalline ceramics have been fabricated by the gas phase condensation technique. The mechanical properties of one of the first ceramics produced by this method, nanophase TiO2, have been discussed in an earlier study.1 This paper reports a similar study undertaken to examine the properties of nanocrystalline ZnO. Nanoindenter techniques are used to determine hardness, Young's modulus, and strain rate sensitivity in ultra-fine grained ZnO. Significant properties variations are experienced within a given sample, indicating a large degree of microstructural inhomogeneity. Nevertheless, a distinct evolution in properties can be observed as a function of sintering temperature. Young's modulus and hardness values increase almost linearly with increasing sintering temperature, and, in addition, there also appears to be a linear correlation between the development of the two materials properties. In contrast, strain rate sensitivity is shown to have an inverse dependence on sintering temperature. This dependence appears to be linked to the strong influence of grain size on strain rate sensitivity, so that the lower sintering temperatures, which provide the finer grain sizes, tend to promote strain rate sensitivity. The results of this study are strikingly similar to those obtained earlier for nanophase TiO2, and they indicate that the earlier results could probably be generalized to a much broader range of nanocrystalline ceramics.

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40

Li, Ming. "THEORETICAL METHODS ON NANOINDENTATION". Chinese Journal of Mechanical Engineering 39, n. 03 (2003): 142. http://dx.doi.org/10.3901/jme.2003.03.142.

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41

Dickinson, M. "Nanoindentation of biological composites". IOP Conference Series: Materials Science and Engineering 4 (1 agosto 2009): 012015. http://dx.doi.org/10.1088/1757-899x/4/1/012015.

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42

Sawa, T., e K. Tanaka. "Nanoindentation of natural diamond". Philosophical Magazine A 82, n. 10 (luglio 2002): 1851–56. http://dx.doi.org/10.1080/01418610208235696.

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43

Tan, E. P. S., e C. T. Lim. "Nanoindentation study of nanofibers". Applied Physics Letters 87, n. 12 (19 settembre 2005): 123106. http://dx.doi.org/10.1063/1.2051802.

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44

Fischer-Cripps,, AC, e DW Nicholson,. "Nanoindentation. Mechanical Engineering Series". Applied Mechanics Reviews 57, n. 2 (1 marzo 2004): B12. http://dx.doi.org/10.1115/1.1704625.

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45

Gotsmann, B., H. Rothuizen e U. Duerig. "Ballistic nanoindentation of polymers". Applied Physics Letters 93, n. 9 (settembre 2008): 093116. http://dx.doi.org/10.1063/1.2977867.

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46

Tadmor, E. B., R. Miller, R. Phillips e M. Ortiz. "Nanoindentation and incipient plasticity". Journal of Materials Research 14, n. 6 (giugno 1999): 2233–50. http://dx.doi.org/10.1557/jmr.1999.0300.

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This paper presents a large-scale atomic resolution simulation of nanoindentation into a thin aluminum film using the recently introduced quasicontinuum method. The purpose of the simulation is to study the initial stages of plastic deformation under the action of an indenter. Two different crystallographic orientations of the film and two different indenter geometries (a rectangular prism and a cylinder) are studied. We obtain both macroscopic load versus indentation depth curves, as well as microscopic quantities, such as the Peierls stress and density of geometrically necessary dislocations beneath the indenter. In addition, we obtain detailed information regarding the atomistic mechanisms responsible for the macroscopic curves. A strong dependence on geometry and orientation is observed. Two different microscopic mechanisms are observed to accommodate the applied loading: (i) nucleation and subsequent propagation into the bulk of edge dislocation dipoles and (ii) deformation twinning.

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47

Adams, M. J., A. Akram, B. J. Briscoe, C. J. Lawrence e D. Parsonage. "Nanoindentation of particulate coatings". Journal of Materials Research 14, n. 6 (giugno 1999): 2344–50. http://dx.doi.org/10.1557/jmr.1999.0311.

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A knowledge of the formation and rupture mechanisms for agglomerates is essential when seeking to model equipment designed to produce and process such materials. In the work described here, nanoindentation of “two-dimensional” agglomerate films, basically particulate coatings, was carried out to establish a means of identifying the generic breakage mechanisms for agglomerates. Selected applied load and penetration depth data in the range (0.02 mN and 700 nm, respectively) are provided as a function of the loading time during continuous loading for a model system composed rather of monodispersed colloidal silica particles (20–24 nm diameter) bound with a poly(methyl methacrylate) at 5 vol%. It is argued that these data enable the sequence of binder bridge failures to be observed, thus giving an indication of the breakage mechanism of the agglomerate and also the strength of the individual junctions. These data are also incorporated into a mechanical model that describes the rupture and deformation behavior of these planar agglomerate systems.

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48

Zhang, Tong-Yi, e Wei-Hua Xu. "Surface Effects on Nanoindentation". Journal of Materials Research 17, n. 7 (luglio 2002): 1715–20. http://dx.doi.org/10.1557/jmr.2002.0254.

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In this paper, we report on a study of the surface effect on nanoindentation and introduce the apparent surface stress that represents the energy dissipated per unit area of a solid surface in a nanoindentation test. The work done by an applied indentation load contains both bulk and surface work. Surface work, which is related to the apparent surface stress and the size and geometry of an indenter tip, is necessary in the deformation of a solid surface. Good agreement is found between theoretical first-order approximations and empirical data on depth-dependent hardness, indicating that the apparent surface stress plays an important role in depth-dependent hardness. In addition, we introduce a critical indentation depth. The surface deformation predominates if the indentation depth is shallower than the critical depth, while the bulk deformation predominates when the indentation depth is deeper than the critical depth.

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Pharr, G. M., e A. Bolshakov. "Understanding nanoindentation unloading curves". Journal of Materials Research 17, n. 10 (ottobre 2002): 2660–71. http://dx.doi.org/10.1557/jmr.2002.0386.

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Experiments have shown that nanoindentation unloading curves obtained with Berkovich triangular pyramidal indenters are usually welldescribed by the power-law relation P = α(h − hf)m, where hf is the final depth after complete unloading and α and m are material constants. However, the power-law exponent is not fixed at an integral value, as would be the case for elastic contact by a conical indenter (m = 2) or a flat circular punch (m = 1), but varies from material to material in the range m = 1.2–1.6. A simple model is developed based on observations from finite element simulations of indentation of elastic–plastic materials by a rigid cone that provides a physical explanation for the behavior. The model, which is based on the concept of an indenter with an “effective shape” whose geometry is determined by the shape of the plastic hardness impression formed during indentation, provides a means by which the material constants in the power law relation can be related to more fundamental material properties such as the elastic modulus and hardness. Simple arguments are presented from which the effective indenter shape can be derived from the pressure distribution under the indenter.

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Kumar, Dinesh, Karamjit Singh, Veena Verma e H. S. Bhatti. "Nanoindentation of Carbon Nanostructures". Journal of Nanoscience and Nanotechnology 16, n. 6 (1 giugno 2016): 6400–6406. http://dx.doi.org/10.1166/jnn.2016.12649.

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